Isotropic metamaterial lens for magnetic imaging applications

Abstract

Examples of the present invention include metamaterial lenses that allow enhanced resolution imaging, for example in MRI apparatus. An example metamaterial may be configured to have μ=−1 along three orthogonal axes. Superior performance was demonstrated using such improved designs, and in some examples, imaging resolution better than λ / 500 was obtained. The use of one or more lumped reactive elements in a unit cell, such as one or more lumped capacitors and / or one or more lumped inductors, allowed unit cell dimensions and hence resolution to be dramatically enhanced. In some examples, a cubic unit cell was used with an essentially isotropic magnetic permeability of μ=−1 obtained at an operating electromagnetic frequency and wavelength (λ).

Description

REFERENCE TO RELATED APPLICATION[0001]This Utility patent application claims priority to U.S. provisional patent application Ser. No. 61 / 481,524, filed May 2, 2011, the content of which is incorporated herein in its entirety.FIELD OF THE INVENTION[0002]The invention relates to metamaterials, including metamaterial lenses used for magnetic resonance imaging applications.BACKGROUND OF THE INVENTION[0003]MRI (magnetic resonance imaging) resolution can be increased by increasing the magnetic field strength, but these higher magnetic field systems are costlier, bulkier, and require additional infrastructure. Hence, it would be desirable to increase resolution without increasing the magnetic field strength. Improved methods and devices for conditioning magnetic field distributions, including imaged fields, would be useful for a variety of applications.SUMMARY OF THE INVENTION[0004]Examples of the present invention include metamaterials configured as 3-dimensional isotropic structures havi...

AI Technical Summary

Benefits of technology

[0007]Measurements of fabricated prototypes confirmed the metamaterial simulations, both in the frequency of operation and in the imaging properties of the lens. Measurements with two closely-spaced loops in the source plane demonstrated both the improved resolution and increased field strength made possible by the lens.

[0008]Example metamaterial lenses allow improved low frequency imaging applications, such as portable MRI systems.

[0009]Advantaged of the metamaterial lenses include resolution improvement in magnetic imaging. Applications also include magnetic field enhancement, for example in field concentration of a magnetic field source, and increased penetration depth for imaging. A lens may be used for enhancing and concentrating the magnetic field, which then can propagate deeper into the body. In some examples, the same lens can be used for field enhancement and for resolution enhancement of the image.

[0012]Example apparatus include nuclear magnetic resonance apparatus, such as a magnetic resonance imaging apparatus. The apparatus may include a magnet providing a static magnetic field, wherein the operating frequency is a nuclear resonance frequency in the nuclear magnetic resonance apparatus, for example a proton magnetic resonance frequency in the static magnetic field. For example, the operating frequency may be a nuclear resonance frequency within an imaged object. A variable magnetic field generator may be used to form, e.g. field gradients for magnetic resonance imaging purposes, as known in the magnetic resonance imaging art. The image resolution of the metamaterial lens may be better (i.e. smaller) than λ / 100, where is the electromagnetic wavelength at the operating frequency. The operating frequency of the apparatus may be in the range 1 MHz to 1 GHz, for example in the range 5 MHz to 500 MHz. A method of improved magnetic resonance imaging of an object in a magnetic field includes locating an isotropic metamaterial lens, such as an example lens described herein, between the object and an imaging sensor. A method of increasing MRI resolution of an imaged object in an MRI apparatus without increasing static magnetic field strength includes introducing an isotropic metamaterial lens as described herein into the MRI apparatus between the imaged object and an imaging sensor, thereby increasing MRI resolution.

Problems solved by technology

MRI (magnetic resonance imaging) resolution can be increased by increasing the magnetic field strength, but these higher magnetic field systems are costlier, bulkier, and require additional infrastructure.

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